package net.chrislehmann.util;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class SerializationUtils
{
   public static <T> List<T> unserializeList(Pattern pattern, String input, Unserializer<T> unserializer)
   {
      List<T> items = new ArrayList<T>();

      Matcher matcher = pattern.matcher( input );

      while ( matcher.find() )
      {
         items.add( unserializer.unserialize( matcher ) );
      }

      return items;
   }

   public static <T> T unserialize(Pattern pattern, String input, Unserializer<T> unserializer)
   {
      T object = null;
      Matcher matcher = pattern.matcher( input );
      if ( matcher.find() )
      {
         object = unserializer.unserialize( matcher );
      }

      return object;
   }


   /**
    * Lifted from http://www.w3.org/International/O-URL-code.html
    * @param s String to decode
    * @return a decoded string
    */
   public static String decode(String s)
   {
      StringBuffer sbuf = new StringBuffer();
      if ( s != null )
      {

         int l = s.length();
         int ch = -1;
         int b, sumb = 0;
         for ( int i = 0, more = -1; i < l; i++ )
         {
            /* Get next byte b from URL segment s */
            switch ( ch = s.charAt( i ) )
            {
               case '%' :
                  ch = s.charAt( ++i );
                  int hb = (Character.isDigit( (char) ch ) ? ch - '0' : 10 + Character.toLowerCase( (char) ch ) - 'a') & 0xF;
                  ch = s.charAt( ++i );
                  int lb = (Character.isDigit( (char) ch ) ? ch - '0' : 10 + Character.toLowerCase( (char) ch ) - 'a') & 0xF;
                  b = (hb << 4) | lb;
                  break;
               case '+' :
                  b = ' ';
                  break;
               default :
                  b = ch;
            }
            /* Decode byte b as UTF-8, sumb collects incomplete chars */
            if ( (b & 0xc0) == 0x80 )
            { // 10xxxxxx (continuation byte)
               sumb = (sumb << 6) | (b & 0x3f); // Add 6 bits to sumb
               if ( --more == 0 )
                  sbuf.append( (char) sumb ); // Add char to sbuf
            }
            else if ( (b & 0x80) == 0x00 )
            { // 0xxxxxxx (yields 7 bits)
               sbuf.append( (char) b ); // Store in sbuf
            }
            else if ( (b & 0xe0) == 0xc0 )
            { // 110xxxxx (yields 5 bits)
               sumb = b & 0x1f;
               more = 1; // Expect 1 more byte
            }
            else if ( (b & 0xf0) == 0xe0 )
            { // 1110xxxx (yields 4 bits)
               sumb = b & 0x0f;
               more = 2; // Expect 2 more bytes
            }
            else if ( (b & 0xf8) == 0xf0 )
            { // 11110xxx (yields 3 bits)
               sumb = b & 0x07;
               more = 3; // Expect 3 more bytes
            }
            else if ( (b & 0xfc) == 0xf8 )
            { // 111110xx (yields 2 bits)
               sumb = b & 0x03;
               more = 4; // Expect 4 more bytes
            }
            else
            /*if ((b & 0xfe) == 0xfc)*/{ // 1111110x (yields 1 bit)
               sumb = b & 0x01;
               more = 5; // Expect 5 more bytes
            }
            /* We don't test if the UTF-8 encoding is well-formed */
         }
      }

      return sbuf.toString();
   }

   public interface Unserializer<T>
   {
      T unserialize(Matcher matcher);
   }
   
   private final static String[] hex = {
      "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07",
      "%08", "%09", "%0a", "%0b", "%0c", "%0d", "%0e", "%0f",
      "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17",
      "%18", "%19", "%1a", "%1b", "%1c", "%1d", "%1e", "%1f",
      "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27",
      "%28", "%29", "%2a", "%2b", "%2c", "%2d", "%2e", "%2f",
      "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37",
      "%38", "%39", "%3a", "%3b", "%3c", "%3d", "%3e", "%3f",
      "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47",
      "%48", "%49", "%4a", "%4b", "%4c", "%4d", "%4e", "%4f",
      "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57",
      "%58", "%59", "%5a", "%5b", "%5c", "%5d", "%5e", "%5f",
      "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67",
      "%68", "%69", "%6a", "%6b", "%6c", "%6d", "%6e", "%6f",
      "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77",
      "%78", "%79", "%7a", "%7b", "%7c", "%7d", "%7e", "%7f",
      "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87",
      "%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f",
      "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97",
      "%98", "%99", "%9a", "%9b", "%9c", "%9d", "%9e", "%9f",
      "%a0", "%a1", "%a2", "%a3", "%a4", "%a5", "%a6", "%a7",
      "%a8", "%a9", "%aa", "%ab", "%ac", "%ad", "%ae", "%af",
      "%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7",
      "%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf",
      "%c0", "%c1", "%c2", "%c3", "%c4", "%c5", "%c6", "%c7",
      "%c8", "%c9", "%ca", "%cb", "%cc", "%cd", "%ce", "%cf",
      "%d0", "%d1", "%d2", "%d3", "%d4", "%d5", "%d6", "%d7",
      "%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df",
      "%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7",
      "%e8", "%e9", "%ea", "%eb", "%ec", "%ed", "%ee", "%ef",
      "%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7",
      "%f8", "%f9", "%fa", "%fb", "%fc", "%fd", "%fe", "%ff"
    };

    /**
     * Encode a string to the "x-www-form-urlencoded" form, enhanced
     * with the UTF-8-in-URL proposal. This is what happens:
     *
     * <ul>
     * <li><p>The ASCII characters 'a' through 'z', 'A' through 'Z',
     *        and '0' through '9' remain the same.
     *
     * <li><p>The unreserved characters - _ . ! ~ * ' ( ) remain the same.
     *
     * <li><p>The space character ' ' is converted into a plus sign '+'.
     *
     * <li><p>All other ASCII characters are converted into the
     *        3-character string "%xy", where xy is
     *        the two-digit hexadecimal representation of the character
     *        code
     *
     * <li><p>All non-ASCII characters are encoded in two steps: first
     *        to a sequence of 2 or 3 bytes, using the UTF-8 algorithm;
     *        secondly each of these bytes is encoded as "%xx".
     * </ul>
     *
     * @param s The string to be encoded
     * @return The encoded string
     */
    public static String encode(String s)
    {
      StringBuffer sbuf = new StringBuffer();
      int len = s.length();
      for (int i = 0; i < len; i++) {
        int ch = s.charAt(i);
        if ('A' <= ch && ch <= 'Z') {     // 'A'..'Z'
          sbuf.append((char)ch);
        } else if ('a' <= ch && ch <= 'z') {  // 'a'..'z'
             sbuf.append((char)ch);
        } else if ('0' <= ch && ch <= '9') {  // '0'..'9'
             sbuf.append((char)ch);
        } else if (ch == ' ') {           // space
             sbuf.append('+');
        } else if (ch == '-' || ch == '_'     // unreserved
            || ch == '.' || ch == '!'
            || ch == '~' || ch == '*'
            || ch == '\'' || ch == '('
            || ch == ')') {
          sbuf.append((char)ch);
        } else if (ch <= 0x007f) {        // other ASCII
             sbuf.append(hex[ch]);
        } else if (ch <= 0x07FF) {        // non-ASCII <= 0x7FF
             sbuf.append(hex[0xc0 | (ch >> 6)]);
             sbuf.append(hex[0x80 | (ch & 0x3F)]);
        } else {                  // 0x7FF < ch <= 0xFFFF
             sbuf.append(hex[0xe0 | (ch >> 12)]);
             sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]);
             sbuf.append(hex[0x80 | (ch & 0x3F)]);
        }
      }
      return sbuf.toString();
    }
}
